It is known to modify the electrical properties of organic semiconductors, in particular their electrical conductivity, by means of doping, as is the case also in respect of inorganic semiconductors, such as silicon semiconductors. Here, the conductivity, which is initially very low, is increased by generating charge carriers in the matrix material, and depending on the type of dopant used a change in the Fermi level of the semiconductor may also be achieved. Doping in this case leads to an increase in the conductivity of charge transport layers, as a result of which ohmic losses are reduced, and to an improved transfer of the charge carriers between the contacts and the organic layer.
The inorganic dopants used to date, such as alkali or alkaline earth metals (e.g. caesium) or Lewis acids (e.g. FeCl3), are usually disadvantageous in the case of organic matrix materials on account of their high diffusion coefficient, since the function and stability of the electronic components is impaired. These inorganic dopants are also associated with difficulties in production, since they usually have a high vapour pressure at room temperature and may contaminate the production systems in vacuum processes. Alkali and alkaline earth metals in particular have the further disadvantage that use thereof is made more difficult on account of their high reactivity to air. It is also known to release dopants in the semiconductive matrix material via chemical reactions, in order to provide dopants. However, the oxidation potential of the dopants released in this way is often not sufficient for various applications, such as in particular for organic light-emitting diodes (OLEDs). Moreover, when the dopants are released, further compounds and/or atoms are also generated, for example atomic hydrogen, as a result of which the properties of the doped layer and of the corresponding electronic component are impaired.
Furthermore, compounds used as dopants often do not have a sufficiently low ionisation potential for the respective application.
The object of the present invention is to provide novel compounds which can he used as n-dopants, as an injection layer or as a blocking layer, wherein the compounds also have sufficiently low oxidation potentials for producing electron transport materials for organic light-emitting diodes, without having any disruptive effect on the matrix material, and are intended to provide an effective increase in the number of charge carriers in the matrix material and are relatively easy to handle.
Further objects of the present invention consist in specifying possible uses of these compounds, in providing organic semiconductive materials and an electronic component or optoelectronic component in which the compounds can be used, e.g. in photoinitiated memories.